Ammonia soda process



Feb 13 1940- N. WINDECKER'E-r Al. 2,189,826

` AMMONIA SODA PROCESS Filed Feb. 21, 1958 3 sheets-sheet 1 3Sheets-Sheet 2 l/L/mesam Lime/@vliz r-Z aan C'Oa Gas ,ln/745e.

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ATTORNEY.

AMMONIA SODA PROCESS Filed Feb. 2l, 1938 C. N. WINDECKER ET AL rr'bonmor2a Gas phase.

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AMMONIA SODA PROCESS s sheets-sheet 3. I

Filed Feb. 21, 1958 /M MMM ATTORNEY.

Patented Feb. 13, `1940 UNITED` r PATENT` OFFICE L l' "'ffnfaissszt'12"`:u: f I

v .f AMMONIA soDArRooEss Clifton N. Winae'c'ier anfa Rbet E.' Winaeeker,l

Painesvillc, `0hio;.'-Robe rt Windecker, llren'eW.' Alonso',v andCharlesEdward. Win'- decker executors of said Clifton N.`*Windecker,

y deceased 'v Application February 21, iasyseriaino. 191,732

Claims. (Cl. d

This invention relates to an ammonia'soda process and has for its objectto provide aprocess which will effect important economies over thestandard ammonia-soda process as .generally` f content as aA source ofat least part; of the carbon l dioxide in the gas phase reactions, andusing mainly vthe substantially pure, vrecovered carbon dioxide gas'inthe liquid-gas contactreaction.

Stated in a somewhat more limited way, `the object is to provide lforthe formation of solid ammonium carbonateand/,or carbamate in a gasphase reaction and for thenutilizing the samebto i., produce sodium.bicarbonate in a liquid `gasconu tact reaction with Sodium chloridein;solution. A further object is to provide for a continuous ammoniasoda process capable of attainingthe above objects and involvingalternate use of two reaction chambers or sets of .reaction chambers forthe production of ammonium carbonate and/or carbamate by a gas phasereaction resulting in `deposit of the reaction-product in solid form inthe chambers, the deposit in onereaction ..0 chamber 4being removed bydissolving in-.brine while a deposit is being formedin the other.` v p eA further object is to provide for carryingy yout the ammoniadistillation partly in aheater section adapted to decompose carbonates(principally ammonium bicarbonate) and partly in a lime section adapted.to recover the ammonia l from ammonium chloride and passing theevolvedgases from the heater section andv from the limehsection to separate gasphase carbonators whereby quired to react with the ammonia from vtheheater 'in thei'ormation of ammonium carbonateia strong gas), beingfreed of ammonia, can be passed to the bicarbonator thereby reducing,and, if suicient care is exercised, nearlyeliminating the need forsupplementary CO2 4from the lime kiln to the-bicarbonator. (This iobjectis achieved inthe variant form illustrated inliig. 2.)

Other and more limited objectswill bein part apparent and in partlpointed out hereinafter, reference being had to theaccompanyingdrawings wherein Fig. 1 is a flow diagram of anammonia sodaprocess embodying thev invention, that part of the flow which isconstant being describe morev inI detail, we bring togethercar-'Iindicated byfull lines and the-intermittent now vdiagram similar tovthat of Fig. 1 V.in thatgases from-the heater and lime section thevexcess CO2 from the heater overthat rebeing illustrated in-brokenlines.By disregarding thev dotted lineal-,and regarding only the full linesandthe` dot-and-.dash lines, the flow will be seencomplete for `oneAportion of the cycle, andH by disregarding the -dot-'and-.dash linesand having regard only to the fulllines and dotted lines l`the flow willbe seen complete for the other portion ofthe cycle; Fig. lab is aragmentof a ilovvl but vdiffering arevreturned to the carbonatorthroughseparate pipesboth of which contain NH3 but only one gram which`is not shown jbeing identical with cess strong COzpk-from Athe heatersection is freed from ammonia and passed tothe bicarbonator;

and Fig. 3 lis a schematic showing of onejsof the gas phase carbonatorsindicated n Figs. 1 and 2; 4. and.showingithe` connections to theWasher,

storage tank, etc, f

In present practice the COzlgasis absorbed in ammoniatednbrine fandreacts with NH3. 'The ratel and extent of the CO2 absorption increaseswith the p-ressureof the mixedgas and also with vthe percentage ofVCOzin the gas. For this reason and'because of the construction oftheequipment y employed, it is usual in present practice to compress thegases to from 21A; to `3 vatmospheres absolutaand it isl thereforedesirable to use a kiln?? gas,rich yin CO2, the production of which hasbeen expensive, requiring coke for v fuel and selected sizes of-stoneand coke.

In our `processthe rst half carbonation is carried out in the gas phase,and

- the necessity for rich. gas and high pressures is y obviated. In thesecond half of the carbonation,

in lwhich ammonium bicarbonate is iormed, rich CO2 gas is used,- which,because of the relatively; small volume requires comparativelylittlefpower fork compression. Since a gas with relatively low ,CO2content canbeutilized in the gas phase reaction, cheap fuels, cheapergrades of limestone andcheaper burningmethods can be employed;and,isince `high, pressure isnot necessaryin the I-gas phase reaction,importantsavings in power may berealized. i .i 1

In carrying out our process, which We will now f the ammonia- ,of `whichcontains CO2, that portion ofthe diad operate at least a few degreesabove that tem perature.

Another important consideration is the quantity of water in the system.In the practice of the ammonia soda process it is desirable to keep thewater content as low as possible in order to increase the efficiency. Tothis end, the brine employed is as nearly saturated as practicallypossible. In our process, we are able to introduce 0.53 pound of waterfor each pound of ammonia, reacting to form carbonate, without dilutingthe brine, since that amount of water is required to form ammoniumcarbonate from NH3, CO2 and H2O. Water is introduced by way of gasesderived from the heater and lime section of the ammonia distiller and byway of kiln gas. The practical way of controlling the moisture contentof these gases is to control their temperature. Since some pipes carrygases containing both NH3 and CO2, their temperature cannot well bereduced below 60 C. Gases in other pipes, however, can have theirmoisture content decreased by lowering their temperature. It isconvenient to cool such pipes to 40 C. in summer and lower in winter. Inaccordance with our process as illustrated in Fig. l, a temperature of40 C. for the kiln gases and 63 C. for the gases from the ammoniadistiller will result in the introduction of .450 pound of H2O per poundof NH3. This is less than the .530 pound required to form all carbonatein the carbonators and some carbavmate will be formed. When this isdissolved in the brine, it not only will not be diluted but thecarbamate will take up water to vform carbonate assisting practically inkeeping up the brine concentration. In the case illustrated in Fig. 1a,

the gas from the lime section can be vcooled even below 40 C. whereby agreater proportion of carbamate will be formed. In the case illustratedin Fig. 2, by controlling the temperature of the gases from the heaterto about 63 C. and the gases from the like kiln and the lime section toabout 40 C., a proportion of carbamate is formed, with the result thatthe brine is not diluted but actually concentrated. The mixture of thesegases at the proper temperature, as indicated above, is passed into areaction chamber which may take the form shown in Fig. 3 where itcontacts surfaces which are cooled to a suitably low temperature wherebysolid ammonium carbonate or carbamate or a mixture thereof is depositedin the reaction chamber. It should be understood that the reaction takesplace when the mixed gases are cooled to below about 60 C. and that thesolids formed may be deposited on the cooling surfaces or on othersurfaces or even to a small extent carried away with the inert gases asdust, and caught in the brine washer. We have found that a deposit ofquite considerable thickness, for example, a quarter of an inch or moremay be thus formed on the copled surfaces, the reaction product havingfairly good heat conducting properties. Only enough power is required topass the gases through the reaction chamber and a low grade source ofcarbon dioxide may be employed, the

in excess of the theoretical amount required to react with the ammoniapresent to form ain-- monium carbonate. We have found that nearly vallthe ammonia will be combined with CO2 to form solid ammonium carbonateor carbamatc, even in the presence of a large proportion of inert gases,and but very little washing will be required to remove any remainingtrace of ammonia in the exit gases. Such ammonia as does pass throughthe reaction chamber into the washer will be absorbed therein by sodiumchloride brine and the inert gases will be vented to the atmosphere by asuitable pump.

After a suitable amount of deposit is formed in the reaction chamber,the brine from the washer (a substantially saturated sodium chloridesolution) is admitted thereto and dissolves the reaction product forminga solution of ammonium carbonate. This solution is conveyed to storagetanks, which are equipped with agitator-s to prevent formation andsettling of large crystals, and where any desired adjustment of am--monia content can be made. This liquor is new admitted into a cooledbicarbonator and there treated with carbon dioxide with agitation, thecarbon dioxide being derived as far as possibie from the decarbonatingfurnace and augmented so far as necessary by kiln gas or strong gas fromsome other source. In this bicarbonator, thc ammonium carbonate combineswith carbon dioxide and forms ammonium bicarbonate which, being in thepresence of sodium chloride, reacts to form sodium bicarbonate andammonium chloride. f

The resulting mixture, containing sodium bicarbonate in suspension, isfiltered and the sodium bicarbonate is passed to the decarbonatingfurnace while the solution containing ammonium chloride, with smaller'proportions of ammonium bicarbonate and. unreacted sodium chloride ispassed to the ammonia distiilcr. From the decarbonating furnace thedesired end product, sodium carbonate, is obtained, while the carbondioxide of high purity is passed to the cooled bicarbonator forconversion of ammonium carbonate to ammonium bicarbonate as previouslyexplained. In the ammonia distiller the ammonium bicarbonate isdecomposed by heat, yielding ammonia gas and CO2, and the ammoniumchloride is reacted upon by lime, forming calcium chloride and releasingammonia. The gases, consisting principally of ammonia, are passedthrough a suitable cooler (or coolers Fig. 1a and Fig. 2) and then tothe reaction chambers for the formation of ammonium carbonate and/orcarbamate as previously explained.

In the ilow diagrams we have shown the flow between the various units ofthe apparatus errployed, indicating how the process is made con--tinuous by using two reaction chambers alter- `constituting the cooledreaction chambers employed herein is illustrated in Fig. 3.

From Fig. 3 it will be seen that we employ a .section oi the ammoniadistiller.

: --aisasae tank orl receptacle I0 provided with .partitions II,formed-deposit 'of ammonium carbonate with `a and I2 deining, with theportions vof the tank proper, `spaces I3 and I4. :These spaceslare'connected by a plurality of tubes I5 whereby cooling water may bepassed for example from the pipe I6 to the space I3, through the pipesI5," to the space Irl. and out through the pipe I1. 1

The kiln gas may enter through a pipe 20 .into the interior of a mixing.chamber 2I which at the same time ,receives ammonia from the'y ammoniadistiller through the pipe 22. Mixing is effected in the chamber 2I by arotating mixing element 23 driven through a pulley 24 orf may beeffected by any other suitableimeans. The mixlture of gasesl then passesinto the unit;;I0 ,where ammonia in the gases is absorbed by the brinewhich is supplied througha suitablepipev 3| .and

drained through pipe28, to reservoir `2l. a: When the carbonator oflFig. 3 has beenN used for the gas phase reaction forsuch a time as toproduce a 4deposit of suitable amount, thegassupply is shut ofi bysuitable valve mechanism` (not shown) and brine from the washeris:admitted from the ybrine-reservoir 21 and pipe. 33. tothe interior ofthe unit Illl where it ,comes into contact with, the deposit therein`and ldissolves the same. The rate of dissolving is, inthe preferredmode of operation, increasedbycirculating the brine through thechamber.` '[I'hiscirculation is effected by Withdrawingit through; ,pipe3.2 to

lpump 34 and again vdeliveringhit-toa unit l.Ill

tion illustrated in Figs. 1EL and 2fas well asin the form illustrated inFig. 1. v v. .f .Y

AReferring now to Fig. l, it will be seen that fuel and limestone, bothof which are productive of carbon dioxide and water vapor, arefed tothelime kiln, a lean carbon dioxide gasI passing lfrom [the lime kilnalternately to the gas phase carbonators, and calcium oxide passing. tolthe `lime Any excess gas produced in the lime kiln is allowedtoescapeto the atmosphere or may be otherwise utilized. As indicated by thedotted lines andthe dotand-dash line going from the Llimekilnto the twocarbonators respectively, thecarbon .dioxide gas from the lime kilnpasses to the right hand carbonatcr during one half of the cycleandztothe left hand Vcarbonator during the other half. l v n s* M Y to forkthe purpose of obtaining a quantity of When the gas is1 passing totheright 'hand carbonator, brine from the washer passes to the leftvhand Garbbnator Where it .dissolves a. lpreviously by the dot-and-dashline. .l stood that'when the carbon dioxide gas is iiow` ing; to eithercarbonator, ammonia from the am' vrnonia distillervis also flowing tothe same cargreater'or less quantity of ammonium carbamate dependingupon the amount of moisturepresent in the gases and contained in thechamber where the deposit is formed. Thus, while a deposit is beingformed in the right hand carbonator, the deposit previously formed inthe left hand carbonator is dissolved and passed in the form of asolution of yammonium carbonate to the bicarbonator. In the other halfcycle, gas flowsv to' the left hand carbonator as indicated by the dot-,and-dash line, while brine iiows from the washer to-the right handcarbonator, as also indicated It will be underbonator;V whereby theconstituent gases for the formation of ammonium carbonate or carbamatewill be present.

`lin the bicarbonator, strong carbon dioxide gas .from 4thedecarbonator, supplemented so far as vis necessaryv by a lean gas fromthe lime kilns, Vreacts with vanimoniumcarbonate and sodium Achloride to-form sodium bicarbonate. s form ofthe invention Aillustrated in Fig. 2,the gas'irom the decarbonator is supplemented by `strong. gas fromn theheater passing through the In thel carbonators 2 and 2a and will requirebut littlel if any kiln gas.

passes to the filter where the solid sodium bicarbonate is separatedfrom the solution and passed4 to the decarbonator there to be converted,into sodium carbonate and a strong carbon dioxide gas which passes backto the bicarbonator monia distiller which is made up of a heatingsection ,labeled Heater `and a lime section. In ,the heating section,the ammonium bicarbonate is broken down to yield ammonia and carbondioxide and in the lime section the ammoniumY `chloride is reacted withlime from the lime kiln.

Thus in vboth sections of the ammonia distiller, ammonia is recoveredand together with carbon dioxide resulting from the breaking down ofamf, monium bicarbonate and with the accompanying.

Water vapori is passed alternately to the gas phase carbonators Wherethe CO2 from the heater is supplemented by enough lean CO2 gas from thelime kiln 'for the correct proportion to form vsolid carbonate ofyammonia. Theinert gas from lthe limev kiln which does not react in thegas phase carbonators passes to the washer for the *recovery of anyammonia content and thence to the atmosphere.

In'Fi'g. 2 we 'have shown a iiow diagram for a' variation of the processillustrated in Fig. l wherein we employ two pairs of gas phase carybonators,I that pairl indicated as I and Ia core,v

responding to the two carbonators of Fig. 1 and thoseindicated as 2 and2a being auxiliary therestrong carbon dioxide gas from the heatingsection' ofthe ammonia distiller. By recovering this;

Ammonium bicarbonate is `be`v lieved to be formed as an intermediateproduct. The sodium bicarbonate in the form of a slurry strong gas andpassing it to the bicarbonator, we are able to reduce to a minimum thequantity of lean gas necessary to be supplied from the lime kiln to thebicarbonator. The required supply of kiln gas to the bicarbonator, beingsmall, indication thereof has, for clarity of illustration, been omittedfrom Fig. 2.

It will be observed that lean gas from the lime kiln fiows alternatelyto carbonators I and la and that ammonium carbonate solution flowsalternately from these carbonators to a. blending tank. At the same timea mixture of ammonia and carbon dioxide passes from the heateralternately to carbonators 2 and 2a, the ammonium carbonate formed byreaction of ammonia and carbon dioxide from the heater flowing as asolution alternately to the blending tank where it is mixed with theammonium carbonate solution from carbonators I and Ia and passed to thebicarbonator. It will be observed that the ammonia and carbon dioxidepassing from the heater to carbonators 2 and 2a is derived principallyfrom the decomposition of ammonium bicarbonate and that therefore'thecarbon dioxide content is approximately double that required to reactwith the ammonia content. Accordingly, approximately half of the carbondioxide, as a strong gas, is freed from ammonia and passed to thebicarbonator to supplement the strong carbon dioxide gas from thedecarbonator. Thus, while the process of Fig. 2 requires additionalequipment, it avoids the undesirable feature of passing lean carbondioxide from the lime kiln to the bicarbonator.

It will be noted that by employing the kiln gas in the gas phasereaction where little power is required and the carbon dioxide of highpurity from the carbonating furnace in the bicarbonator, substantialsavings in power are eiected as compared with the usual method ofabsorbing ammonia in the `brine and then treating the resulting solutionwith the yentire quantity of carbon dioxide, necessitating theexpenditure of energy for forcing the inert gases through a liquid-gascontact reaction. This method makes unnecessary any special eiorts toproduce kiln gases of high carbon dioxide content and the cheapestmethods of lime burning are available. We also effect substantialsavings in the amount of cooling water required since highertemperatures can be used in the formation of the ammonium carbonate andcarbamate than those employed in the standard carbonating tower.

This is a continuation in part of our copending application Serial No.162,462, filed September 4, 1937.

Having thus described our invention, what we claim is:

l. An ammonia-soda process comprising the steps of rst, bringingtogether ammonia and carbon dioxide gases and water vapor in theproportion two mols of ammonia, approximately one mol of carbon dioxideand less than one mol of water, second, cooling the mixture untilsubstantially all the ammonia has combined'with carbon dioxide to formammonium carbonate or ammonium carbamate, third, dissolving theresulting solid in a substantially saturated sodium chloride solution,fourth, contacting the resulting solution with carbon dioxide whereby toproduce sodium bicarbonate andammonium chloride, fth, separating thesolid sodium bicarbonate thus produced from the ammonium chlorideliquor, sixth, converting said solid sodium bicarbonate to sodiumcarbonate and carbon dioxide and returning the carbon dioxide thusproduced to y the fourth step, and seventh, recovering ammonia andreturning the same to the rst step.

2. .'[n the combination recited in claim l, the first two 4steps beingcarried out in one reaction Ichamber for a time and then in anotherreaction chamber for a time, and the third step following thediscontinuance of the second in each reaction chamber, whereby thecomplete process may be continuously performed.

3. An ammonia-soda process comprising the steps of first, bringingtogether ammonia and carbon dioxide gases and water vapor in theproportion two mols of ammonia, approximately one mol of carbon dioxideand less than one mol water, second, Vcooling the mixture untilsubstantially all the ammonia has combined with carbon dioxide to formsolid ammonium carbonate or carbamate, third, dissolving the resultingsolid in a substantially saturated solution of sodium chloride, fourth,contacting the resulting solution with carbon dioxide to produce sodiumbicarbonate, fifth, separating the reaction mixture into a rst portionconsisting principally of sodium bicarbonate and a second portioncontaining substantially all the ammonium chloride and unreacted sodiumchloride and a material quantity of ammonium bicarbonate, in solution,sixth, converting the sodium bicarbonate to sodium carbonate and carbondioxide and returning the carbon dioxide to the fourth step, seventh,recovering carbon dioxide from said second portion by heating andreturning a part of such carbon dioxide to the fourth step, and eighth,recovering ammonia from the ammonium chloride by addition of Ca(OH)2 andreturning the same to the rst step.

4. An ammonia-soda process comprising the steps of rst, bringingtogether ammonia and carbon dioxide gases and water vapor in theproportion of approximately two mols of ammonia, one mol of carbondioxide and less than one mol water, second, cooling the mixture untilsubstantially all the ammonia has combined with carbon dioxide to formsolid ammonium carbonate or carbamate, third, dissolving the resultingsolid in a substantially saturated solution of sodium chloride, fourth,contacting the resulting solution with carbon dioxide in the proportionof not less than one mol CO2 to two mols NH3, fifth, separating thereaction mixture into a rst portion consisting principally of solidsodium bicarbonate and a second portion containing substantially all theammonium chloride and unreacted sodium chloride and a material quantityof ammonium bicarbonate, in solution, sixth, converting the sodiumbicarbonate to sodium carbonate and carbon dioxide and returning thecarbon dioxide to the fourth step, seventh, heating said second portionto cause evolution of a mixture of ammonia and carbon dioxide gases,eighth, cooling the last mentioned mixture until substantially all theammonia therein has been converted to solid ammonium carbonate orcarbamate and passing the excess carbon dioxide to the fourth step, andninth, recovering ammonia from the ammonium chloride and returning thesame to the rst step.

5. An ammonia-soda process comprising the steps of rst, bringingtogether ammonia and CO2, said ammonia being at a temperature notexceeding that at which ammonia and carbon dioxide form a solid, saidcarbon dioxide being moist and at a temperature not greatly exceeding 40C., the proportions of ammonia, carbon diing the resulting solution withcarbon dioxider 10 whereby to produce sodium bicarbonate and ammoniumchloride,` fth, separating the solid so'- dium bicarbonate thus producedfrom the ammonium chloride liquor, sixth, converting said solid sodiumbicarbonate to sodium carbonate and carbon dioxide and returning thecarbon dioxide thus produced to the fourth step, and seventh,

recovering ammonia and returning the same to the rst step.

l CLIFTON N. WINDECKER. ROBERT E. WINDECKER.

